Microsoft is loosening the reins on Vista licensing in an effort to let businesses try out some new computing possibilities, including "diskless" PCs.

For the most part, the Windows licensing terms have assumed that the whole PC is going to be in one place; however, increasingly, that's not necessarily the case.

Virtualization technology means that one physical computer can act as many separate computers, while higher-speed networks mean that different parts of a computer can actually be housed in various locales. For example, it is now possible to have a diskless PC, in which the main hard drive of the computer is actually stored in a data center, while all the other parts--processor, graphics chip and memory--remain at a worker's desk.

But until Sunday, there was no proper way to license Windows for such a computer. Under new licensing terms for Windows Vista Enterprise, businesses will be able to use the corporate edition of the operating system to handle this as well as other niche cases in which a PC's storage, computational power or both are handled somewhere other than the desktop.

"We're responding to enable a set of early adopters in finance and governments, in particular, to take advantage of architectures that centralize Windows," said Scott Woodgate, director of Windows Business Group. "They either centralize the storage of Windows, the execution of Windows, or both, in the data center."

In addition to the diskless PC, the other arrangement Microsoft is giving the nod to is one in which a desktop PC or thin client is running multiple virtual machines that are running on a server. The Vista Enterprise license already provides a license for additional Windows virtual machines, but only those running on a desktop PC, not for ones taking place on a server. The new approach, called Vista Enterprise Centralized Desktop, requires an additional annual fee.

Although Microsoft is making such set-ups legally permissible, it doubts diskless PCs will become an overnight trend. There are many negatives, most importantly the need for a constant and uninterrupted high-speed network connection. If the network goes down, the whole PC becomes unusable. Also, while Microsoft is making diskless PCs commercially possible, enterprises will still needed additional third-party software to actually make such systems boot up.

Because of the technical limitations and the massive IT resources needed to manage such an operation, Microsoft expects only a small number of institutions to try out such a set-up, most likely top-secret government agencies where security concerns trump the inconveniences.

"If you are in a department that is a three-letter department you may want to keep that hard drive away," Woodgate said, likely making reference to places like the CIA or FBI. "It's relatively a niche."

Even in those cases, Microsoft says it will take time to get the systems up and running. "It will be interesting to see, 18 to 24 months after those early adopters have taken the systems into production, how successful they are," Woodgate said.

About the author

During her years at CNET News, Ina Fried has changed beats several times, changed genders once, and covered both of the Pirates of Silicon Valley. These days, most of her attention is focused on Microsoft. E-mail Ina.
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